I've been having horrible headaches for the past 4 days. It comes from the left side of my neck and just shoots into my head. It seems to hurt at the beat of my heart. It isn't just on and off pain, but all day. I go to sleep with it, I wake up with it, and it is a horrible pain. If I push down on the spot on my neck, i feel pain also. Can anyone tell me what this could be?